The development of coordinated singing in cooperatively displaying long-tailed
manakins.

Abstract: Long-tailed manakins (Chiroxiphia linearis)
have a puzzling social system in which teams of two males display cooperatively
in
dispersed lek arenas, but only the alpha partner mates with visiting
females. One benefit of performing as a nonmating partner
might be to gain experience as an ‘‘apprentice’’ to improve the performance
of the complex duet song and joint dance. We
examined the relationship between the age of singers and two measures
of singing performance: song variability and sound
frequency matching. Singing performance improved with age; variability
in four song characteristics of males less than 3 years
old was greater than that in their older partners, and frequency matching
increased with the age of the younger partner.
Randomization tests of song samples from seven well-established teams
showed that males did not track the song-to-song variation
in their partners’ singing. Another randomization test showed that
frequency matching by these teams was higher than that of
randomly paired partners. We considered three alternative hypotheses
for the congruent songs: (1) short-term accommodation
to the partner’s song; (2) active choice of partners with similar intrinsic
frequencies; and (3) long-term development of congruent
song through either practice or song copying. Our results and evidence
from long-term monitoring of banded birds
best support the hypothesis that frequency matching develops over several
years during the complex and protracted process of
partner formation. Nonmating males may benefit from increasing their
competence at display, eventually enjoying increased
mating success when they inherit display sites from older males. Key
words: age, Chiroxiphia, cooperation, learning, lek, manakin,
Pipridae, sexual selection, song, suboscine, vocal development. [Behav
Ecol 13:65?69 (2002)]